在asp中避免PostBack

Question

我希望在我的按钮事件触发时避免回发。由于回发，我的列表再次变空。请帮我解决这个问题。我该怎么做才能避免回发。我正在使用ASP按钮。

这是我的按钮方法

id = Convert.ToInt32(Request.QueryString["id"].ToString());


                venues.Add(id);

                foreach (int item1 in venues)
                {



                    if (!hashset.Add(item1))
                    {
                        Response.Write("<script>alert('Duplicate Items');</script>");
                        break;
                    }

                    else
                    {

                        foreach (var items in venues)
                        {
                            con.Open();
                            SqlCommand cmd = con.CreateCommand();
                            cmd.CommandType = CommandType.Text;
                            cmd.CommandText = "select * from Venues where VenueID = '" + items + "'";
                            cmd.ExecuteNonQuery();
                            DataTable dt = new DataTable();
                            SqlDataAdapter ds = new SqlDataAdapter(cmd);
                            ds.Fill(dt);
                            foreach (DataRow dr in dt.Rows)
                            {
                                Name = dr["Name"].ToString();
                                Address = dr["Address"].ToString();
                                Picture = dr["Picture"].ToString();
                                Price = dr["Price"].ToString();
                            }
                            con.Close();
                            if (Request.Cookies["aa"] == null)
                            {
                                Response.Cookies["aa"].Value = Name.ToString() + "," + Address.ToString() + "," + Picture.ToString() + "," + Price.ToString();
                                Response.Cookies["aa"].Expires = DateTime.Now.AddDays(1);

                            }
                            else
                            {
                                Response.Cookies["aa"].Value = Request.Cookies["aa"].Value + "|" + Name.ToString() + "," + Address.ToString() + "," + Picture.ToString() + "," + Price.ToString();
                                Response.Cookies["aa"].Expires = DateTime.Now.AddDays(1);
                            }
                        }
                    }
                }

            }